The use of copper and copper alloys for heat exchange surfaces is common practice because of their improved thermal conductivity. However, these materials are susceptible to aqueous corrosion. In addition, the corrosion of copper alloys can also lead to accelerated corrosion rates throughout the entire system as the salts from the corroded heat exchangers come in contact with ferrous components creating galvanic corrosion cells.
For decades, industrial water treatment practitioners have used aromatic azoles to reduce corrosion rates experienced by copper alloys. Perhaps the most commonly used aromatic azoles available to the industrial water treatment practitioner in today's market are benzotriazole and tolyltriazole. In addition to the aromatic azoles, industrial water treatment practitioners also typically include one or more polymeric dispersants and phosphonates in the additive formulations to improve the overall performance and to keep systems running efficiently. Examples of such prior art systems and formulations may be found in, for example, U.S. Pat. Nos. 4,197,210; 4,464,276; 4,642,221; 5,035,720 and 5,800,732, the contents of which are incorporated herein, in their entirety, by reference.
The aqueous formulation of aromatic azoles at percentage levels (>1%) in a water treatment formulation typically requires that the formulation pH be either alkaline (pH>12) for tolyltriazole derivatives or acidic (pH<2) for benzotriazole derivatives. This leads to finished product formulations generally having a hazardous pH, either strongly acidic or strongly basic which then relates to increased storage and shipping requirements. The addition of acidic or basic salts used to modify pH also effectively decreases product concentration while increasing product weight. The combination of acids and bases are also associated with heat generation during product manufacture which tends to increase both costs and manufacturing cycle time. In 40 C.F.R. §261.22, the EPA defines a substance as being corrosive if “it is aqueous and has a pH less than or equal to 2 or greater than or equal to 12.5 . . . .” The U.S. Department of Transportation (“DOT”) also allows the use of this definition to determine whether a substance is to be considered hazardous for transport in commerce.
Further enhancement of corrosivity classifications can be studied in regard to corrosivity towards membranes such as skin. Corrositex™ distributed by InVitro International is an in vitro test that determines chemical corrosivity and permits assignment of Packing Group classification for Class 8 corrosives. This test replaces the rabbit test of dermal corrosivity by providing a reliable means of mimicking this test. The proprietary core technology of the Corrositex™ test is based upon a biomembrane and chemical detection system, which becomes colored when exposed to potentially corrosive substances. It is highly desirable that water treatment formulations are not corrosive by both of these classification methods.
The additive compositions encompassed by the present disclosure reduce corrosivity, allow for increased concentration of actives, and reduces or eliminates the need to use either potash or caustic soda or mineral acids such as sulfuric or hydrochloric acid by providing a formulation that exhibits increased stability at significantly more moderate, i.e., non-corrosive, pH values. (pH>2-pH<12)
Further, the elimination of mineral acid or caustic soda or potash allows for improved manufacturing time intervals by reducing the time, equipment and/or energy required to dissipate the heat of neutralization.